Dynamic downlink reuse in a C-RAN

ABSTRACT

This disclosure is directed to various ways to dynamically manage the subset of radio points that are used to transmit to user equipment in a C-RAN.

REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/567,658, filed on Oct. 3, 2017, which is herebyincorporated herein by reference in its entirety.

BACKGROUND

A centralized radio access network (C-RAN) is one way to implement basestation functionality. Typically, for each cell implemented by a C-RAN,a single baseband unit (BBU) interacts with multiple remote units (alsoreferred to here as “radio points” or “RPs”) in order to providewireless service to various items of user equipment (UEs).

As used here, “reuse” refers to situations where separate downlink dataintended for multiple UEs is simultaneously transmitted to the UEs usingthe same resource elements (that is, the same time-frequency resource).Typically, these situations arise when the UEs are sufficientlyphysically separated from each other so that the different downlinktransmissions do not interfere with each other when transmitted fromdiffering subsets of RPs. This type of reuse is also referred to as“spatial reuse.”

Conventional techniques for implementing spatial reuse are oftenrelatively simplistic or conservative, which can result in relativelyfew opportunities to employ spatial reuse, in spatial reuse beingemployed in inappropriate situations (for example, due to one or more ofthe UEs moving), and/or spatial resource degrading overall systemperformance.

SUMMARY

One embodiment is directed a system to provide wireless service. Thesystem comprises a controller and a plurality of radio points. Each ofthe radio points is associated with at least one antenna and remotelylocated from the controller, wherein the plurality of radio points iscommunicatively coupled to the controller. The controller and theplurality of radio points are configured to implement a base station inorder to provide wireless service to a plurality of user equipment (UEs)using a cell. The controller is communicatively coupled to a corenetwork of a wireless service provider. The system is configured totransmit at least some data to each UE connected to the cell using arespective subset of the radio points. The system is configured todetermine the respective subset of the radio points for transmitting toeach UE connected to the cell using a signature vector comprising a setof signal reception metrics, each signal reception metric associatedwith a respective one of the radio points and indicative of thereception of a signal transmitted from the respective UE at one of theradio points. The system is configured to do the following when each UEestablishes a new connection with the cell: determine initial signalreception metrics for that UE; and if the system has a stored signaturevector associated with that UE and that stored signature vector matchesthe initial signal reception metrics for that UE, initialize thesignature vector for that UE using that stored signature associated withthat UE.

Another embodiment is directed to a system to provide wireless service.The system comprises a controller and a plurality of radio points. Eachof the radio points is associated with at least one antenna and remotelylocated from the controller, wherein the plurality of radio points iscommunicatively coupled to the controller. The controller and theplurality of radio points are configured to implement a base station inorder to provide wireless service to a plurality of user equipment (UEs)using a cell. The controller is communicatively coupled to a corenetwork of a wireless service provider. The system is configured to dothe following for each UE connected to the cell: determine a signaturevector comprising a set of signal reception metrics, each signalreception metric associated with a respective one of the radio pointsand indicative of the reception of a signal transmitted from therespective UE at one of the radio points; determine a respective minimumsubset of the radio points for transmitting to that UE; determine arespective maximum subset of the radio points for transmitting to thatUE; and determine a respective current subset of the radio points fortransmitting to that UE based on, at least, the signature vector, therespective minimum subset of the radio points for transmitting to thatUE, and the respective maximum subset of the radio points fortransmitting to that UE. The system is configured to, for each UEconnected to the cell, expand the number of radio points in the minimumsubset of the radio points if the respective signature vector for thatUE has not been updated at least a predetermined number of times. Thesystem is configured to wirelessly transmit at least some data to eachUE connected to the cell using the respective current subset of theradio points determined for that UE based.

Another embodiment is directed to a system to provide wireless service.The system comprises a controller and a plurality of radio points. Eachof the radio points is associated with at least one antenna and remotelylocated from the controller, wherein the plurality of radio points iscommunicatively coupled to the controller. The controller and theplurality of radio points are configured to implement a base station inorder to provide wireless service to a plurality of user equipment (UEs)using a cell. The controller is communicatively coupled to a corenetwork of a wireless service provider. The system is configured to dothe following for each UE connected to the cell: determine a signaturevector comprising a set of signal reception metrics, each signalreception metric associated with a respective one of the radio pointsand indicative of the reception at one of the radio points of a signaltransmitted from the respective UE; determine a respective minimumsubset of the radio points for transmitting to that UE; determine arespective maximum subset of the radio points for transmitting to thatUE; and determine a respective current subset of the radio points fortransmitting to that UE based on, at least, the signature vector, therespective minimum subset of the radio points for transmitting to thatUE, and the respective maximum subset of the radio points fortransmitting to that UE. The system is configured to, for each UEconnected to the cell, update the respective current subset of the radiopoints used to transmit that UE based on at least one of the following:at least one ratio of the actual rate of throughput for at least one UEconnected to the cell and an estimated rate of throughput for said atleast one UE connected to the cell; at least one processing load at theradio points; and demand from at least one UE connected to the cell touse at least one radio point. The system is configured to wirelesslytransmit at least some data to each UE connected to the cell using therespective current subset of the radio points determined for that UE.

DRAWINGS

FIG. 1 is a block diagram illustrating one exemplary embodiment of aradio access network (RAN) system in which the dynamic reuse techniquesdescribed here can be implemented.

FIG. 2 comprises a flow chart illustrating one exemplary embodiment of amethod of dynamically maintaining a signature vector in a C-RAN.

FIG. 3 comprises a flow chart illustrating one exemplary embodiment of amethod of determining a minimum simulcast zone and a maximum simulcastzone for a UE in a C-RAN.

FIGS. 4A-4B comprise a flow chart illustrating one exemplary embodimentof a method of dynamically managing a simulcast zone for a UE in aC-RAN.

FIGS. 5A-5B comprise a flow chart illustrating one exemplary embodimentof a method of dynamically managing a link adaptation variable used toinitialize and dynamically update the modulation and coding scheme (MCS)used to communicate with a UE in a C-RAN.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 1 is a block diagram illustrating one exemplary embodiment of aradio access network (RAN) system 100 in which the dynamic reusetechniques described here can be implemented. The system 100 is deployedat a site 102 to provide wireless coverage and capacity for one or morewireless network operators. The site 102 may be, for example, a buildingor campus or other grouping of buildings (used, for example, by one ormore businesses, governments, other enterprise entities) or some otherpublic venue (such as a hotel, resort, amusement park, hospital,shopping center, airport, university campus, arena, or an outdoor areasuch as a ski area, stadium or a densely-populated downtown area).

In the exemplary embodiment shown in FIG. 1 , the system 100 isimplemented at least in part using a C-RAN (point-to-multipointdistributed base station) architecture that employs at least onebaseband unit 104 and multiple radio points (RPs) 106 serve at least onecell 103. The system 100 is also referred to here as a “C-RAN system”100. The baseband units 104 are also referred to here as “basebandcontrollers” 104 or just “controllers” 104. Each RP 106 includes or iscoupled to one or more antennas 108 via which downlink RF signals areradiated to user equipment (UE) 110 and via which uplink RF signalstransmitted by UEs 110 are received.

More specifically, in the example shown in FIG. 1 , each RP 106comprises two antennas 108. Each RP 106 can include or be coupled to adifferent number of antennas 108.

The system 100 is coupled to the core network 112 of each wirelessnetwork operator over an appropriate back-haul. In the exemplaryembodiment shown in FIG. 1 , the Internet 114 is used for back-haulbetween the system 100 and each core network 112. However, it is to beunderstood that the back-haul can be implemented in other ways.

The exemplary embodiment of the system 100 shown in FIG. 1 is describedhere as being implemented as a Long Term Evolution (LTE) radio accessnetwork providing wireless service using an LTE air interface. LTE is astandard developed by 3GPP standards organization. In this embodiment,the controller 104 and RPs 106 together are used to implement an LTEEvolved Node B (also referred to here as an “eNodeB” or “eNB”) that isused to provide user equipment 110 with mobile access to the wirelessnetwork operator's core network 112 to enable the user equipment 110 towirelessly communicate data and voice (using, for example, Voice overLTE (VoLTE) technology).

Also, in this exemplary LTE embodiment, each core network 112 isimplemented as an Evolved Packet Core (EPC) 112 comprising standard LTEEPC network elements such as, for example, a mobility management entity(MME) (not shown) and a Serving Gateway (SGW) (not shown) and,optionally, a Home eNodeB gateway (HeNB GW) (not shown) and a SecurityGateway (SeGW) (not shown).

Moreover, in this exemplary embodiment, each controller 104 communicateswith the MME and SGW in the EPC core network 112 using the LTE Siinterface and communicates with other eNodeBs using the LTE X2interface. For example, the controller 104 can communicate with anoutdoor macro eNodeB (not shown) via the LTE X2 interface.

Each controller 104 and the radio points 106 can be implemented so as touse an air interface that supports one or more of frequency-divisionduplexing (FDD) and/or time-division duplexing (TDD). Also, thecontroller 104 and the radio points 106 can be implemented to use an airinterface that supports one or more of themultiple-input-multiple-output (MIMO), single-input-single-output(SISO), single-input-multiple-output (SIMO),multiple-input-single-output (MISO), and/or beam forming schemes. Forexample, the controller 104 and the radio points 106 can implement oneor more of the LTE transmission modes. Moreover, the controller 104and/or the radio points 106 can be configured to support multiple airinterfaces and/or to support multiple wireless operators.

In the exemplary embodiment shown in FIG. 1 , the front-haul thatcommunicatively couples each controller 104 to the one or more RPs 106is implemented using a standard ETHERNET network 116. However, it is tobe understood that the front-haul between the controllers 104 and RPs106 can be implemented in other ways.

Generally, one or more nodes in a C-RAN perform analog radio frequency(RF) functions for the air interface as well as digital Layer 1, Layer2, and Layer 3 (of the Open Systems Interconnection (OSI) model)functions for the air interface.

In the exemplary embodiment shown in (L1) FIG. 1 , each basebandcontroller 104 comprises Layer-3 (L3) functionality 120, Layer-2 (L2)functionality 122, and Layer-1 (L1) functionality 124 configured toperform at least some of the Layer-3 processing, Layer-2 processing, andLayer-1 processing, respectively, for the LTE air interface implementedby the RAN system 100, and each RP 106 includes (optionally) Layer-1functionality (not shown) that implements any Layer-1 processing for theair interface that is not performed in the controller 104 and one ormore radio frequency (RF) circuits (not shown) that implement the RFfront-end functions for the air interface and the one or more antennas108 associated with that RP 106.

Each baseband controller 104 can be configured to perform all of thedigital Layer-3, Layer-2, and Layer-1 processing for the air interface,while the RPs 106 (specifically, the RF circuits) implement only the RFfunctions for the air interface and the antennas 108 associated witheach RP 106. In that case, IQ data representing time-domain symbols forthe air interface is communicated between the controller 104 and the RPs106. Communicating such time-domain IQ data typically requires arelatively high data rate front haul. This approach (communicatingtime-domain IQ data over the front haul) is suitable for thoseimplementations where the front-haul ETHERNET network 116 is able todeliver the required high data rate.

If the front-haul ETHERNET network 116 is not able to deliver the datarate needed to front haul time-domain IQ data (for example, where thefront-haul is implemented using typical enterprise-grade ETHERNETnetworks), this issue can be addressed by communicating IQ datarepresenting frequency-domain symbols for the air interface between thecontrollers 104 and the RPs 106. This frequency-domain IQ datarepresents the symbols in the frequency domain, in the downlink, beforethe Inverse Fast Fourier Transform (IFFT) is performed and, in theuplink, after the Fast Fourier Transform (FFT). The time-domain IQ datacan be generated by quantizing the IQ data representing thefrequency-domain symbols without guard band zeroes or any cyclic prefixand communicating the resulting compressed, quantized frequency-domainIQ data over the front-haul ETHERNET network 116. Additional detailsregarding this approach to communicating frequency-domain IQ data can befound in U.S. patent application Ser. No. 13/762,283, filed on Feb. 7,2013, and titled “RADIO ACCESS NETWORKS,” which is hereby incorporatedherein by reference.

Where frequency-domain IQ data is front-hauled between the controllers104 and the RPs 106, each baseband controller 104 can be configured toperform all or some of the digital Layer-3, Layer-2, and Layer-1processing for the air interface. In this case, the Layer-1 functions ineach RP 106 can be configured to implement the digital Layer-1processing for the air interface that is not performed in the controller104.

Where the front-haul ETHERNET network 116 is not able to deliver thedata rate need to front haul (uncompressed) time-domain IQ data, thetime-domain IQ data can be compressed prior to being communicated overthe ETHERNET network 116, thereby reducing the data rate neededcommunicate such IQ data over the ETHERNET network 116.

Data can be front-hauled between the controllers 104 and RPs 106 inother ways (for example, using front-haul interfaces and techniquesspecified in the Common Public Radio Interface (CPRI) and/or Open BaseStation Architecture Initiative (OBSAI) family of specifications).

Each controller 104 and RP 106 (and the functionality described as beingincluded therein) can be implemented in hardware, software, orcombinations of hardware and software, and the various implementations(whether hardware, software, or combinations of hardware and software)can also be referred to generally as “circuitry” or a “circuit”configured to implement at least some of the associated functionality.When implemented in software, such software can be implemented insoftware or firmware executing on one or more suitable programmableprocessors. Such hardware or software (or portions thereof) can beimplemented in other ways (for example, in a field programmable gatearray (FPGA), application specific integrated circuit (ASIC), etc.).Also, the RF functionality can be implemented using one or more RFintegrated circuits (RFICs) and/or discrete components. Each controller104 and RP 106 can be implemented in other ways.

In the exemplary embodiment shown in FIG. 1 , a management system 118 iscommunicatively coupled to the controllers 104 and RPs 106, for example,via the Internet 114 and ETHERNET network 116 (in the case of the RPs106).

In the exemplary embodiment shown in FIG. 1 , the management system 118communicates with the various elements of the system 100 using theInternet 114 and the ETHERNET network 116. Also, in someimplementations, the management system 118 sends and receives managementcommunications to and from the controllers 104, each of which in turnforwards relevant management communications to and from the RPs 106.

As noted above, “reuse” refers to situations where separate downlinkdata intended for two (or more) different UEs 110 is simultaneouslytransmitted to the UEs 110 using the same resource elements. Typically,these situations will arise when the UEs 110 are sufficiently physicallyseparated from each other so that the different downlink transmissionsdo not interfere with each other when transmitted from differing subsetsof RPs 106. Also, as noted above, this type of reuse is also referred toas “spatial reuse.”

For each UE 110 that is attached to the cell 103, the controller 104assigns a subset of the RPs 106 to that UE 110, where the RPs 106 in thesubset are used to transmit to that UE 100. This subset of RPs 106 isreferred to here as the “simulcast zone” for that UE 110.

In the exemplary embodiment described here in connection with FIG. 1 ,the simulcast zone for each UE 110 is determined by the servingcontroller 104 using a “signature vector” (SV) associated with that UE110. In this embodiment, a signature vector is determined for each UE110. The signature vector is determined based on receive powermeasurements made at each of the RPs 106 serving the cell 103 for uplinktransmissions from the UE 110.

When a UE 110 makes initial LTE Physical Random Access Channel (PRACH)transmissions to access the cell 103, each RP 106 will receive thoseinitial PRACH transmissions and a signal reception metric indicative ofthe power level of the PRACH transmissions received by that RP 106 ismeasured (or otherwise determined). One example of such a signalreception metric is a signal-to-noise plus interference ratio (SNIR).The signal reception metrics that are determined based on the PRACHtransmissions are also referred to here as “PRACH metrics.”

Each signature vector is determined and updated over the course of thatUE's connection to the cell 103 based on Sounding Reference Signals(SRS) transmitted by the UE 110. A signal reception metric indicative ofthe power level of the SRS transmissions received by the RPs 106 (forexample, a SNIR) is measured (or otherwise determined). The signalreception metrics that are determined based on the SRS transmissions arealso referred to here as “SRS metrics.”

Each signature vector is a set of floating pointsignal-to-interference-plus-noise ratio (SINR) values (or other metric),with each value or element corresponding to a RP 106 used to serve thecell 103.

The signature vector can be used to determine the RP 106 having the bestsignal reception metric by scanning or sorting the elements of thesignature vector to find the element having the best signal receptionmetric. The RP 106 that corresponds to that “best” element is alsoreferred to here as the “primary RP 106” for the UE 110.

A “quantized signature vector” (QSV) is also determined for each UE 110.The QSV for each UE 100 is a vector that includes an element for each RP106, where each element has one of a finite set of values. For example,the element for each RP 106 has a first value (for example, a value of“1”) if the corresponding RP 106 is included in the simulcast zone forthat UE 110 and has second value (for example, a value of “0”) if thecorresponding RP 106 is not included in the simulcast zone for that UE110. The QSV for each UE 110 can be determined using the SV for that UE110.

The QSVs for the UEs 110 can be used to conveniently determine if thesimulcast zones of two UEs 110 do not include any of the same RPs 106.That is, the QSVs for two UEs 110 can be used to conveniently determineif the simulcast zones for the two UEs 110 are disjoint. If this is thecase, the simulcast zones for the UEs 110 (and the UEs 110 themselves)are referred to here as being “orthogonal” to each other. This can bedone, for example, applying a logical “AND” operation on correspondingelements of the two QSVs.

If the simulcast zones for two UEs 110 are orthogonal to each other,then those UEs 110 are candidates for spatial reuse since differentdownlink transmissions can be simultaneously transmitted from thedisjoint sets of RPs 106 to the UEs 110. In general, fewer RPs 106 inthe simulcast zone of a UE 110 likely results in more opportunities forthat UE 110 to be put into reuse with another UE 110 connected to thesame cell 103 and higher overall system throughput with the trade-offthat each UE 110 might experience more interference or lower throughput.Conversely, more RPs 106 in the simulcast zone of a UE 110 likelyresults in fewer opportunities for that UE 110 to be put into reuse withanother UE 110 connected to the same cell 103 and lower overall systemthroughput with the trade-off that the UE 110 might experience lessinterference or higher airlink throughput.

As used here, “expanding” a QSV or a simulcast zone refers to increasingthe number of RPs 106 in the simulcast zone, and “contracting” a QSV orsimulcast zone refers to reducing the number of RPs 106 in the simulcastzone.

In the exemplary embodiment described here in connection with FIG. 1 ,the serving controller 104 is configured to manage the signature vectorsQSVs for the UEs 110 connected to the cell 103.

FIG. 2 comprises a flow chart illustrating one exemplary embodiment of amethod 200 of dynamically maintaining a signature vector in a C-RAN. Theembodiment of method 200 shown in FIG. 2 is described here as beingimplemented in the C-RAN system 100 of FIG. 1 , though it is to beunderstood that other embodiments can be implemented in other ways.

The blocks of the flow diagram shown in FIG. 2 have been arranged in agenerally sequential manner for ease of explanation; however, it is tobe understood that this arrangement is merely exemplary, and it shouldbe recognized that the processing associated with method 200 (and theblocks shown in FIG. 2 ) can occur in a different order (for example,where at least some of the processing associated with the blocks isperformed in parallel and/or in an event-driven manner).

Method 200 is described here as being performed for each UE 110 when itattaches to the cell 103 and establishes an RRC connection. Theparticular UE 110 for which method 200 is being performed is referred tohere as the “current” UE 110.

When the current UE 110 establishes a new RRC connection with the cell103 (block 202), a signal reception metric (such as the SINR) isdetermined from the associated PRACH transmissions at each RP 106 (block204).

If the serving controller 104 has a stored SV for the current UE 110(checked in block 206), the serving controller 104 checks if there is asufficient match between the stored SV and the determined PRACH metrics(block 208). If there is, the current SV is initialized using the storedSV (block 210).

For example, the current UE's SAE-Temporary Mobile Subscriber Identity(S-TMSI) can be used to check if there is a stored SV for the current UE110 and retrieve that stored SV if there is one.

In one implementation, the stored SV for the current UE 110 is sorted indescending order, where SV_(j) denotes the jth element of the currentUE's stored SV and RP_(j) denotes the RP 106 corresponding to the jthelement of the current UE's stored SV. In this implementation, theserving controller 104 determines that there is a sufficient matchbetween the stored SV and the PRACH metrics if all of the following aretrue:

-   -   The elapsed time since the last update of the stored SV during        the current UE's previous RRC connection is less than a        configurable setting (referred to here as “StoredSvMaxAge”);    -   The PRACH transmission is detected by the primary RP 106 of the        stored SV (for example, the PRACH signal reception metric for        the primary RP 106 is above a predetermined threshold);    -   The PRACH transmission is detected by the RP 106 having the next        best reception metric in the stored SV (the “second” RP 106), if        the difference between the reception metric for the primary RP        106 and the reception metric for the second RP 106 is less than        a configurable value (referred to here as        “deltaSvForPrachMatch”); and    -   When at least two RPs 106 detect the PRACH transmission, the two        RPs 106 with the highest PRACH reception metric must be among        the RPs 106 having the top three reception metrics in the stored        SV.

If these conditions are all true, it is determined that there is asufficient match between the stored SV and the PRACH metrics and thecurrent SV is initialized using the stored SV.

When the first SRS transmission from the current UE 110 is received(checked in block 212), if the current SV has not been initialized witha stored SV for the current UE 110 (checked in block 214), the currentSV is initialized using the SRS reception metrics determined for theinitial SRS transmission at each RP 106 (block 216). If the current SVhas been initialized with a stored SV for the current UE 110, thecurrent SV is re-initialized by combining the stored SV with the SRSreception metrics determined for the initial SRS transmission at each RP106 (block 218). In this exemplary embodiment, the stored SV is combinedwith the SRS reception metrics using a relative weighting that dependson the elapsed time since the last update in the current UE's previousRRC connection. In one implementation, the combining using a relativeweighting is done as follows:New SV=Stored SV*(1−min(Δt/(StoredSvMaxAge+ΔT _(init)),1))+SRSSV*Δt/(StoredSvMaxAge+ΔT _(init))

where Δt is the elapsed time since the last update of the stored SV forthe current UE 110 during the current UE's previous RRC connection andΔT_(init) is the typical time elapsed between the PRACH transmission fora UE 110 and the first SRS transmission for the UE 110 (which isnominally set to 240 milliseconds).

Each time a subsequent SRS transmission is received from the current UE110 (checked in block 220), the SV for the current UE 110 is updated(block 222). In one implementation, each element of the current SV isupdated by calculating a moving average that is a function of the SRSreception metrics for the corresponding RP 106.

In this exemplary embodiment, every time an RRC re-connection occurs forthe current UE 110, the current SV for the current UE 110 is retainedand used without re-initialization.

When the current RRC connection is complete (checked in block 224), thecurrent SV for the current UE 110 is stored for possible later retrievaland use as described above (block 226).

In one implementation, each time a subsequent SRS transmission from thecurrent UE 110 is received and the current SV for the current UE 110 isupdated by calculating a moving average that is a function of the SRSreception metrics at each RP 106, a noise-floor-compensated version ofthe SV is generated for the current UE 110 from the original,uncompensated version of the SV for the current UE 110.

The noise-floor-compensated SV for the current UE 110 can be created asfollows. In the following discussion, the original, uncompensated SV isdenoted avgSV=[s(1), . . . , s(Nrp)], where the elements of avgSV aresorted in descending (from best to worst average signal receptionmetric), N_(rp) is the number of RPs 106, and s(1) is the elementcorresponding to the primary RP 106 for the current UE 110.

The corresponding noise-floor-compensated average SV is determined by:avgSV_tilde=[s_tilde(1), . . . ,s_tilde(N _(rp))],

where:

s_tilde(m)=Min(s(m), s(1)−(m−1)×d), where m>=k_hat

d=Max((s(1)−s(k_hat−1))/(k_hat−2),(s(1)−s(k_hat))/(k_hat−1))

k_hat is the index of the first RP 106 having a corresponding element inthe sorted avgSV that is significantly influenced by the noise floor.That is, k_hat is the index of the first RP 106 having a correspondingelement in the sorted avgSV for which both of the following are true:

-   -   variance([s(k_hat) . . . s(N_(rp))])<=VarianceThreshold    -   variance([s(k_hat−1) . . . s(N_(rp))])>VarianceThreshold

In one implementation, the value of VarianceThreshold is set to 1.0

FIG. 3 comprises a flow chart illustrating one exemplary embodiment of amethod 300 of determining a minimum simulcast zone and a maximumsimulcast zone for a UE in a C-RAN. The embodiment of method 300 shownin FIG. 3 is described here as being implemented in the C-RAN system 100of FIG. 1 , though it is to be understood that other embodiments can beimplemented in other ways.

The blocks of the flow diagram shown in FIG. 3 have been arranged in agenerally sequential manner for ease of explanation; however, it is tobe understood that this arrangement is merely exemplary, and it shouldbe recognized that the processing associated with method 300 (and theblocks shown in FIG. 3 ) can occur in a different order (for example,where at least some of the processing associated with the blocks isperformed in parallel and/or in an event-driven manner).

Method 300 is described here as being performed for each UE 110 that isconnected to the cell 104 when the SV for the UE 110 is updated. Theparticular UE 110 for which method 300 is being performed is referred tohere as the “current” UE 110.

As used here, a “minimum QSV” or “MinQSV” for a given UE 110 is theminimum number of RPs 106 that should be in that UE's simulcast zone.Also, a “maximum QSV” or “MaxQSV” for a given UE 110 is the maximumnumber of RPs 106 that should be in that UE's simulcast zone.

In this embodiment, the elements of the SV are sorted in descendingorder from the element having the best metric to the element having theworst metric. Then, a simulcast zone including a given number N of RPs106 can be determined from the sorted SV by including in the simulcastzone the RPs 106 that correspond to the first N entries of the sortedSV. Therefore, the simulcast zone that includes the number of RPs 106specified by the MinQSV includes the first N entries of the sorted SV,where N equals the number specified by the MinQSV. This simulcast zoneis also referred to here simply as the “MinQSV simulcast zone” or justthe “MinQSV.” Likewise, the simulcast zone that includes the number ofRPs 106 specified by the MaxQSV includes the first N entries of thesorted SV, where N equals the number specified by the MaxQSV. Thissimulcast zone is also referred to here simply as the “MaxQSV simulcastzone” or just the “MaxQSV.”

When the current UE 110 establishes a new RRC connection to the cell 103(block 302), the maximum QSV and minimum QSV for the current UE 110 areset to the full simulcast zone (block 304). That is, the maximum QSV andminimum QSV are both set to include the full number of RPs 106 that areused to serve the cell 103.

When the SV for the current UE 110 is initialized or updated in responseto the receipt of an SRS transmission from the current UE 110 (block306), the maximum QSV and minimum QSV for the current UE 110 aredetermined (block 308).

In this embodiment, the maximum QSV and minimum QSV are determined usinga metric, SIR_(PL). For a given candidate simulcast zone, the SIR_(PL)for that simulcast zone is defined as the ratio S/I, where S is the sumof the elements of the sorted current SV that correspond to the RPs 106in the associated candidate simulcast zone and I is the sum of theremaining elements of the sorted current SV.

More specifically, SIR_(PL,j) represents the SIR_(PL) for a candidateQSV with a simulcast zone size of j, where 1⇐j⇐J and J is the totalnumber of RPs 106 used to the serve the cell 103. Each candidate QSV hasan associated candidate simulcast zone, which includes the j RPs 106that have the best signal reception metrics in the current SV.

For example, SIR_(PL1) represents the SIR_(PL) for a simulcast zone thatonly includes the primary RP 106 for the current UE 110. SIR_(PLJ)represents the SIR_(PL) for the full simulcast zone that includes all ofthe RPs 106 that are used to serve the cell 103.

Each SIR_(PLj) is determined based on the current SV for the UE 110.Each time the SV for the UE 110 is initialized or updated in response toreceiving a SRS transmission, the various values of SIR_(PLj) aredetermined using the updated SV.

Then, the minimum QSV, MinQSV, is computed as the QSV with the smallestindex j for which SIR_(PL,j)>Min_SIR, and the maximum QSV, MaxQSV, iscomputed as the QSV with the smallest index j for whichSIR_(PL,j)>Max_SIR. If the smallest index j that satisfies therespective inequalities for MinQSV and MaxQSV is greater than aconfigurable maximum allowed simulcast zone size, SZ_max_allowed, thenthe MinQSV and/or the MaxQSV are reduced to the maximum allowedsimulcast zone size. Also, if the smallest index j that satisfies therespective inequalities for MinQSV and MaxQSV is less than aconfigurable minimum allowed simulcast zone size, SZ_min_allowed, thenthe MinQSV and/or the MaxQSV are increased to the minimum allowedsimulcast zone size.

Min_SIR and Max_SIR are configurable parameters that must satisfy thecondition Max_SIR>=Min_SIR. If MaxSIR=MinSIR=the total number of RPs 106used to serve the cell 103, then reuse is effectively disabled since thefull simulcast zone must be used.

In the exemplary embodiment shown in FIG. 3 , if the SV for the currentUE 110 was not initialized based on a Stored SV (checked in block 310),then the minimum QSV for the current UE 110 determined above inconnection with block 308 is expanded (block 314) until a predeterminednumber of SRS transmissions have been used to update the SV for the UE110 (checked in block 312). By doing this, a more conservative minimumQSV (that is, a larger minimum QSV) is used for the current UE 110 whilethe SV is based on only a relatively small number of SRS transmissions.

In one implementation, the minimum QSV is expanded by a progressivelydecreasing amount until the predetermined number of SRS transmissionshave been used to update the SV. For example, a phased-approach based ontwo configurable parameters, can be used. These two configurableparameters include a first parameter, R_(QSV), which is a configurableparameter used to determine by how much the minimum QSV is to beexpanded in each phase, and the second parameter, N_(SRS), is aconfigurable parameter used to determine the duration of each phase.

In this example, until the SV for the current UE 110 has been updatedbased on a number of received SRS transmissions that equals N_(SRS),each time the minimum QSV is updated in connection with block 308, theresulting minimum QSV is expanded by a number RPs 106 equal to R_(QSV).Thereafter, until the SV for the current UE 110 has been updated basedon an additional number of received SRS transmission equal to N_(SRS),each time the minimum QSV is updated in connection with block 308, theresulting minimum QSV is expanded by a number of RPs 106 equal to themaximum of R_(QSV)−2 or 0 (that is, Max(R_(QSV)-2,0)). Thereafter, untilthe SV for the current UE 110 has been updated based on an additionalnumber of received SRS transmission equal to N_(SRS), each time theminimum QSV is updated in connection with block 308, the resultingminimum QSV is expanded by a number of RPs 106 equal to the maximum ofR_(QSV)-4 or 0 (that is, Max(R_(QSV)-4,0)). After this point, theresulting minimum QSV is no longer expanded.

The processing associated with blocks 306-314 is repeated until the RRCconnection is complete.

In the exemplary embodiment described here in connection with FIG. 1 ,link adaption is used to initialize and dynamically update themodulation and coding scheme (MCS) and the current QSV (cQSV) for eachUE 110 that is connected to the cell 103.

FIGS. 4A-4B comprise a flow chart illustrating one exemplary embodimentof a method 400 of dynamically managing a simulcast zone for a UE in aC-RAN. The embodiment of method 400 shown in FIGS. 4A-4B is describedhere as being implemented in the C-RAN system 100 of FIG. 1 , though itis to be understood that other embodiments can be implemented in otherways.

The blocks of the flow diagram shown in FIGS. 4A-4B have been arrangedin a generally sequential manner for ease of explanation; however, it isto be understood that this arrangement is merely exemplary, and itshould be recognized that the processing associated with method 400 (andthe blocks shown in FIGS. 4A-4B) can occur in a different order (forexample, where at least some of the processing associated with theblocks is performed in parallel and/or in an event-driven manner).

Method 400 is described here as being performed for each UE 110 that isconnected to the cell 103. The particular UE 110 for which method 400 isbeing performed is referred to here as the “current” UE 110.

As described below, at the end of each RRC connection by a given UE 110with the cell 103, the most recent cQSV is stored for possible use withthe UE's next RRC connection.

When the current UE 110 establishes a new RRC connection to the cell 103(block 402 shown in FIG. 4A) and the serving controller 104 hasdetermined that there is a stored SV for the current UE 110 and there isa sufficient match between the stored SV and the PRACH metric determinedfor the new RRC connection (block 404), the cQSV for the current UE 110is initialized using the stored cQSV for the current UE 110 (block 406).Otherwise, the cQSV is initialized without using a stored cQSV for thecurrent UE 110 (block 408).

In this exemplary embodiment, when the SV is initialized with a storedSV (and therefore there is a corresponding stored cQSV), the cQSV isinitialized as follows. A first candidate QSV (QSV1), which has acorresponding candidate simulcast zone, is found that satisfies thefollowing conditions.

First, minQSV⇐QSV1⇐Stored cQSV, where, in this case, “QSV1” representsthe number of RPs 106 in the simulcast zone associated with QSV1 and“Stored cQSV” represents the number of RPs 106 in the simulcast zoneassociated with the Stored cQSV.

Second, no RP_(j) in the candidate simulcast zone associated with QSV1has a L_(sum)(j)>Init_Load-Thr, where L_(sum)(j) is the cumulative load(based on a sliding window) associated with the processing at RP_(j) ofall Resource Block Units (RBUs) allocated to all UEs 110 that have thatRP_(j) in their simulcast zone, and Init_Load-Thr is a configurable loadthreshold.

If both those conditions are satisfied, then the first candidate QSV1 isused as the cQSV for the current UE 110 unless SIR(QSV1)<SIR(storedcQSV)−configSIRLoss1. If that latter condition is satisfied, a secondcandidate QSV2 is found that satisfies the following conditions:QSV2>QSV1 such that SIR(QSV2)>=SIR(stored cQSV)−configSIRLoss1, where“QSV1” represents the number of RPs 106 in the simulcast zone associatedwith QSV1, “QSV2” represents the number of RPs 106 in the simulcast zoneassociated with QSV2, and configSIRLoss1 is a configurable thresholdparameter. If a second candidate QSV2 is found that satisfies thiscondition, the second candidate QSV2 is used as the cQSV for the currentUE 110.

In this exemplary embodiment, when the SV is not initialized with astored SV (and, therefore, the cQSV for the current UE 110 is notinitialized with a stored cQSV for the current UE 110), the cQSV isinitialized as follows. A first candidate QSV (QSV1), which has acorresponding a candidate simulcast zone, is found that satisfies thefollowing conditions.

First, minQSV⇐QSV1⇐maxQSV, where, in this case, “QSV1” represents thenumber of RPs 106 in the simulcast zone associated with QSV1.

Second, no RPj in the simulcast zone associated with QSV1 has aL_(sum)(j)>Init_Load-Thr.

If both those conditions are satisfied, then the first candidate QSV1 isused as the cQSV for the current UE 110 unlessSIR(QSV1)<SIR(maxQSV)−configSIRLoss2. If that latter condition issatisfied, a second candidate QSV2 is found that satisfies the followingconditions: QSV2>QSV1 such that SIR(QSV2)>=SIR(storedcQSV)−configSIRLoss2, where configSIRLoss2 is a configurable thresholdparameter and configSIRLoss2>configSIRLoss1. If a second candidate QSV2is found that satisfies this condition, the second candidate QSV2 isused as the cQSV for the current UE 110.

Method 400 further comprises, after initialization of the cQSV,determining when to update the cQSV for the current UE 110 (block 410).In this exemplary embodiment, the cQSV for the current UE 110 is updatedperiodically using a period P_(cqsv) that is determined as the followingratio: Rank Report Period/NumQSVOppPerRankRep, where Rank Report Periodis the period used by UEs 110 in reporting their Rank Indication (RI) tothe serving controller 104 (in milliseconds) and NumQSVOppPerRankRep isa configurable parameter indicating the number of opportunities toupdate the cQSV for each Rank Report Period (for example, this can beset to an integer of 1, 2, or 4). In one example, default values of 160milliseconds and 2, respectively, can be used for Rank Report Period andNumQSVOppPerRankRep, and the minimum allowed value for the periodP_(cqsv) is 40 milliseconds.

In this exemplary embodiment, the UE's first cQSV update opportunity fora given RRC connection occurs as early as possible subject to thefollowing conditions: The first condition is that the first cQSV updateopportunity will not occur before the SV and cQSV are initialized. Morespecifically, when SV and cQSV have not yet been not initialized uponS-TMSI retrieval, the first cQSV update opportunity will not occur untilafter the first SRS transmission from the current UE 110 has beenreceived. The second condition is that, after the current UE's cQSV hasbeen initialized, the current UE's first CQI report following a rankreport will always coincide with a cQSV update opportunity, such thatthere is never a rank change between two cQSV update opportunities.

Method 400 further comprises, when it is determined that the currentUE's cQSV should be updated, checking whether the cQSV for the currentUE 110 is currently admissible (block 412) and, if the cQSV for thecurrent UE 110 is determined to be inadmissible, modifying the cQSV forthe current UE 110 to be admissible (block 414). If the cQSV is modifiedat this point, the forced expansion flag for the current UE 110(described below) is cleared (block 416), the related metrics areupdated (block 418), and the processing for the current cQSV updateopportunity is complete.

As noted above, there are J candidate QSVs, where the j-th candidateQSV, QSV_(j), is the one having a simulcast zone containing the j RPs106 with the best signal reception metric as reflected in themost-recent SV for the current UE 110. As used here, “jmin” and “jmax”represent values for the index j of the candidate cQSV associated withthe current UE's minQSV and maxQSV, respectively. The candidate QSVbased on the most-recent SV having an index jmin has a simulcast zonecontaining a number of RPs 106 equal to the minQSV for the current UE110. This candidate QSV is also referred to here simply as the “minQSV”in the context of discussing particular candidate QSVs. The candidateQSV based on the most-recent SV having an index jmax has a simulcastzone containing a number of RPs 106 equal to the maxQSV for the currentUE 110. This candidate QSV is also referred to here simply as the“maxQSV” in the context of discussing particular candidate QSVs.

The set of admissible candidate QSVs for the current UE 110 comprisesthe candidate QSVs {jmin, . . . , jmax}. A cQSV is deemed admissible if,based on the most-recent SV for the current UE 110, it is included inthis set of admissible candidate QSVs for the current UE 110 and isdeemed inadmissible if this is not the case. In this embodiment, thecurrent UE's cQSV remains admissible (and is not changed at this point)even if the ordering of the RPs 106 in the most-recent SV has changedsince the last cQSV-update opportunity, as long as the cQSV is stillincluded in the set of admissible candidate QSVs based on themost-recent SV.

Since the SRS transmissions will not be aligned with cQSV updateopportunities, it is possible for a change in the SV for the current UE110 to cause the current UE's cQSV to become temporarily inadmissible inbetween two cQSV update opportunities, and in this case, theinadmissibility will not be detected or corrected until a subsequentcQSV update opportunity.

When a cQSV for the current UE 110 is deemed inadmissible at a cQSVupdate opportunity, the inadmissibility is corrected immediately bysetting the cQSV equal to the candidate QSV included in the set ofadmissible candidate QSVs determined based on the most-recent SV thathas the smallest index j, such that: SIR_(PL,j)>=SIR_(PL), whereSIR_(PL) was the SIR of the current cQSV when it was last deemedadmissible and SIR_(PL,j) is the SIR of the candidate QSV having indexj. When no candidate QSV included in the set of admissible candidateQSVs satisfies the above inequality, the cQSV for the current UE 110 isset to the maxQSV for the current UE 110.

Method 400 further comprises, if the cQSV for the current UE 110 isdetermined to be admissible, updating load calculations for any changesin minQSV for the current UE 110 (block 420). As noted above inconnection with FIG. 3 , the minQSV is updated and changed from time totime. At each cQSV update opportunity for the current UE 110, whetherthe current UE's minQSV has changed since the last cQSV updateopportunity for the current UE 110 is checked. If it has, the loadcalculations for those RPs 106 that are affected by the change in theminQSV are updated. Specifically, if the current UE's minQSV has changedby adding one or more new RPs 106 to the simulcast zone associated withthe minQSV, the load calculation for each of those RPs 106 is increasedby the additional load associated with the current UE 110, and if thecurrent UE's minQSV has changed by removing one or more RPs 106 from thesimulcast zone associated with the minQSV, the load calculation for eachof those RPs 106 is decreased by the load associated with the current UE110.

Method 400 further comprises checking if the cQSV for the current UE 110should be forced to expand (block 422). If that is the case, a forcedexpansion of the cQSV for the current UE 110 is performed (block 424).In this exemplary embodiment, there is a flag (also referred to here asthe “force expansion flag”) maintained for each connected UE 110 thatindicates whether a forced expansion of the cQSV should be performed forthat UE 110 during the next update opportunity. Also, in thisembodiment, there is a variable maintained for each connected UE 110that indicates when the last forced expansion was performed for that UE110. A configurable parameter indicates by how many RPs 106 the minQSVis expanded when a forced expansion is performed.

If a forced expansion of the cQSV for the current UE 110 is performed,the forced expansion flag for the current UE 110 is cleared (block 416),the related metrics are updated (block 418), and the processing for thecurrent cQSV update opportunity is complete.

In some situations, the SINR actually experienced in the channel for thecurrent UE 110 may be much lower than the estimated SINR, due to, forexample, inaccuracies in SRS measurements and, as a result, theresulting SV. The UE's cQSV simulcast zone in such circumstances may notcontain all the RPs 106 it should to provide a sufficiently high SIR. Insuch a situation, the current UE 110 may experience a high block errorratio (BLER) or be provided throughput much lower than desired. Toaddress such issues, the cQSV for the current UE 110 can be flagged fora forced expansion.

In one implementation, such a situation can be identified (and thecurrent UE 110 flagged for a forced expansion) if one of the followingoccurs: the current UE 110 receives two consecutive negativeacknowledgments (NACKs) for third retransmissions, the current UE 110receives two consecutive NACKs for first transmissions made using apower level below a configurable floor, or the current UE 110 receivestwo consecutive NACKs for first transmissions made using a MCS of 0.

In one implementation, the cQSV for the current UE 110 may not becontracted after a forced expansion for a configurable hysteresis periodof time after the forced expansion is performed. In such animplementation, the processing associated with determining if the cQSVfor the current UE 110 should be contracted is skipped until theconfigurable hysteresis period has elapsed after the forced expansion.

Method 400 further comprises, if the cQSV for the current UE 110 shouldnot be forced to expand, determining if the current UE 110 has a validRateRatio (checked in block 426). If that is the case, a contractioneligibility metric and an expansion eligibility metric for the cQSV ofthe current UE 110 are computed (block 428) and the eligibility of thecurrent UE 110 for contraction and expansion of its cQSV is tested(block 430). Then, if indicated by the testing, the cQSV for the currentUE 110 is changed as indicated (block 432) and the related metrics areupdated (block 418) and the processing for the current cQSV updateopportunity is complete. Otherwise, method 400 proceeds to block 434(which is described below).

As noted above, an estimate of the ratio between a connected UE's actualachieved rate and its average virtual CQI rate (adjusted to include linkadaptation noise) is calculated for the current UE 110. A UE's actualachieved rate reflects the effect of reuse interference, whereas theaverage virtual CQI rate represents the achievable rate without reuseinterference. Thus, a higher ratio indicates a lower amount of reuseinterference, whereas a lower ratio indicates a higher amount of reuseinterference. This estimated ratio is also referred to here as the“RateRatio.”

In this exemplary embodiment, for each RP_(j), one UE 110 that has thatRP_(j) in its cQSV is identified as the UE 110 most eligible forcontraction for that RP_(j). To track this, a contraction eligibilitymetric threshold and UE identifier are maintained for each RP_(j) of thecell 103, where the UE identifier is an identifier associated with theUE 110 that is most eligible for contraction (for example, the RNTI ofthat UE 110) and the contraction eligibility metric threshold is themost recent value of the contraction eligibility metric for thatmost-eligible UE 110.

In one implementation, the contraction eligibility metric for thecurrent UE 110 is computed by estimating the change in total airlinkthroughput after the contraction of the cQSV of the current UE 110 byremoving various numbers of the outermost RPs 106 from the current UE'scQSV. Then, the maximum estimated change in the throughput andprocessing load, as well as the maximum contraction demand (described inbelow), are found for the various RPs 106 that are candidates forcontraction. The contraction eligibility metric for the current UE 110is determined based on the maximum estimated change in total airlinkthroughput, the maximum estimated change in the processing load, themaximum contraction demand, and the RateRatio for the current UE 110.

It is noted, however, that in this implementation, any resultingcontraction of the cQSV for the current UE 110 is limited to only to theoutermost RP 106 in the cQSV. As used here, a number of “outermost” RPs106 of a cQSV refers to that number of RPs 106 in the cQSV that have thelowest signal reception metrics in the most-recent SV. Also, thiscomputation is subject to the minQSV. That is, the current UE's cQSV isnot eligible to be contracted below its minQSV.

In such an implementation, the eligibility of the current UE 110 forcontraction of its cQSV is tested by first checking the outermost RP 106for the current UE's cQSV to see if the current UE 110 is the onemost-eligible for contraction for that RP 106. This is determined bycomparing the identifier of the current UE 110 to the identifier of themost eligible UE 110 for that outermost RP 106. If they do not match,then the computed contraction eligibility metric for the current UE 110is compared with the contraction eligibility metric threshold for theoutermost RP 106 in the current UE's cQSV. If the computed contractioneligibility metric for the current UE 110 is greater than thecontraction eligibility metric threshold for the outermost RP 106 in thecurrent UE's cQSV, the current UE 110 becomes the one that is mosteligible for contraction for that outermost RP 106 and the contractioneligibility metric threshold for that outermost RP 106 is updated to bethe computed contraction eligibility metric for the current UE 110.Otherwise, there is no change.

If there is a match between the identifier for the current UE 110 andthe identifier of the UE 110 that is most-eligible for contraction forthe outermost RP 106, then the computed contraction eligibility metricfor the current UE 110 is compared to the contraction eligibility metricthreshold for that outermost RP 106 to see if the computed contractioneligibility metric for the current UE 110 is greater than or equal toconfigurable percentage of the contraction eligibility metric thresholdfor that outermost RP 106 and if the computed contraction eligibilitymetric for the current UE 110 is greater than a configurable minimummargin value. If both of those conditions are true, then the current UE110 is flagged for contraction and the contraction eligibility metricthreshold and most-eligible UE 110 for contraction for the outermost RP106 are both cleared. Otherwise, the contraction eligibility metricthreshold for the outermost RP 106 is updated to be set to the computedcontraction eligibility metric for the current UE 110.

Similar processing if performed for expansion.

In this exemplary embodiment, for each RP_(j), one of the UE's 110 thathas that RP_(j) in its cQSV is identified as the UE 110 that is mosteligible for expansion. To track this, an expansion eligibility metricthreshold and UE identifier is maintained for each RP_(j) of the cell103, where the UE identifier is an identifier associated with the UE 110that is most eligible for expansion (for example, the RNTI of that UE110) and the expansion eligibility metric threshold is the most recentvalue of the expansion eligibility metric for that most-eligible UE 110.

In one implementation, the expansion eligibility metric for the currentUE 110 is computed by estimating the change in total airlink throughputafter the expansion of the cQSV of the current UE 110 by various numbersof the next potential RPs 106 that are not currently in the current UE'scQSV. Then, the maximum estimated change in the throughput andprocessing load, as well as the maximum contraction demand (described inbelow), are found for the various RPs 106 that are candidates forexpansion. The expansion eligibility metric for the current UE 110 isdetermined based on the maximum estimated change in total airlinkthroughput, the maximum estimated change in the processing load, themaximum contraction demand, and the RateRatio for the current UE 110.This computation is subject to the maxQSV. That is, the current UE'scQSV is not eligible to be expanded above its maxQSV.

It is noted, however, that in this implementation, any resultingexpansion of the cQSV is limited to only the next potential RP 106 thatis not in the current UE's cQSV. As used here, a number of “nextpotential” RPs 106 for a cQSV refers to that number of RPs 106 that arenot in the cQSV that have the highest signal reception metrics in themost-recent SV.

In such an implementation, the eligibility of the current UE 110 forexpansion of its cQSV is tested by first checking the next potential RP106 for the current UE's cQSV to see if the current UE 110 is the onethat is the most-eligible for expansion for the next potential RP 106.This is determined by comparing the identifier of the current UE 110 tothe identifier of the UE 110 that is most-eligible for expansion for thenext potential RP 106. If they do not match, then the computed expansioneligibility metric for the current UE 110 is compared with the expansioneligibility metric threshold for the next potential RP 106 in thecurrent UE's cQSV. If the computed expansion eligibility metric for thecurrent UE 110 is greater than the expansion eligibility metricthreshold for the next potential RP 106 in the current UE's cQSV, thecurrent UE 110 is set to be the one most eligible for expansion for thatRP 106 and the expansion eligibility metric threshold for that RP 106 isupdated to be the computed expansion eligibility metric for the currentUE 110. Otherwise, there is no change.

If there is a match between the identifier for the current UE 110 andthe identifier of the UE 110 that is most-eligible for expansion for thenext potential RP 106, then the computed expansion eligibility metricfor the current UE 110 is compared to the expansion eligibility metricthreshold for that next potential RP 106 to see if the computedexpansion eligibility metric for the current UE 110 is greater than orequal to a configurable percentage of the expansion eligibility metricthreshold for that RP 106 and if the computed expansion eligibilitymetric for the current UE 110 is greater than a configurable minimummargin value. If both of those conditions are true, then the current UE110 is flagged for expansion and the expansion eligibility metricthreshold and most-eligible UE 110 for expansion for the next potentialRP 106 are both cleared. Otherwise, the expansion eligibility metricthreshold for the next potential RP 106 is updated to be set to thecomputed expansion eligibility metric for the current UE 110.

Then, after the contraction and expansion eligibility metrics for thecurrent UE 110 are computed, if the current UE's cQSV is flagged forcontraction but not for expansion, the current UE's cQSV is contractedfrom its outermost RP 106.

If the current UE's cQSV is not flagged for contraction but is flaggedfor expansion, the current UE's cQSV is expanded into its next potentialRP 106.

If the current UE's cQSV is flagged for both contraction and expansion,the computed contraction and expansion eligibility metrics are compared.If the contraction eligibility metric is greater than the expansioneligibility metric plus a configurable margin, the current UE's cQSV iscontracted from its outermost RP 106. If the expansion eligibilitymetric is greater than the contraction eligibility metric plus aconfigurable margin, the current UE's cQSV is expanded into its nextpotential RP 106. Otherwise, the current UE's cQSV is not changed.

If the current UE's cQSV is not flagged for contraction or forexpansion, the current UE's cQSV is not changed.

As noted above, in one implementation, the cQSV for the current UE 110may not be contracted for a configurable hysteresis period of time aftera forced expansion has occurred. In such an implementation, theprocessing described above for determining if the cQSV for the currentUE 110 should be contracted is skipped until the configurable hysteresisperiod has elapsed after a forced expansion has occurred.

Method 400 further comprises updating the contraction demand for the RPs106 in the current UE's minQSV (block 434). After this is done, thevarious metrics are updated (block 418) and the processing for thecurrent cQSV update opportunity is complete.

As used here, the “expanded RPs” 106 for a given UE 110 are those RPs106 that are in the UE's cQSV but not in the UE's minQSV, and the“minQSV RPs” 106 for a given UE 110 are those RPs 106 that are in theUE's minQSV. Also, as used here, a UE 110 has “expanded onto” a RP 106if the UE 110 has expanded its cQSV beyond its minQSV to include that RP106, which is not in the UE's minQSV.

A “contraction demand” refers to a metric indicative of the backlog fora UE 110 experienced at the UE's minQSV RPs 106. In this embodiment, thecontraction demand is indicative of the maximum number of resource blockunits (RBUs) the UE 110 could utilize at the UE's minQSV RPs 106 if allother UEs 110 that have expanded onto those RPs 106 contracted theircQSVs to no longer include those RPs 106. The contraction demand is usedto determine if other UEs 110 that have expanded onto those RPs 106should contract their cQSVs in order to remove those RPs 106 from theircQSVs.

The following variables are maintained for each RP 106 serving the cell103: a contraction demand variable, a UE identifier variable, a ratevariable, and an expiry timer variable. The UE identifier variable isused to identify the UE 110 that includes that RP 106 in its minQSV thatis experiencing the heaviest backlog. This identifier can be, forexample, the RNTI of the UE 110. The contraction demand variable is usedto store the contraction demand metric for the identified UE 110. Therate variable is used to store the estimated actual achieved rate forthe identified UE 110. The expiry timer variable is used to indicatewhen the other variables should expire and no longer be used.

If the cQSV for the current UE 110 has not changed at the current updateopportunity, then the backlog experienced by the current UE 110 at itsminQSV RPs 106 is checked to see if it is greater that a configurablebacklog threshold. If it is, the contraction demand metric for thecurrent UE 110 is updated and then each of the current UE's minQSV RPs106 is checked. For each of the current UE's minQSV RPs 106, if the UEidentifier maintained for that RP 106 does not match the current UE'sidentifier, then if the contraction demand metric for the current UE 110is greater than the one stored in the contraction demand variable ofthat RP 106, then the variables maintained for that RP 106 are updatedwith the current UE's identifier, contraction demand metric, andestimated actual achieved rate, and the expiry timer variable for thatRP 106 is reset.

For each of the current UE's minQSV RPs 106, if the UE identifiermaintained for that RP 106 does match the current UE's identifier, thenthe variables maintained for that RP 106 are updated with the currentUE's contraction demand metric and estimated actual achieved rate, andthe expiry timer variable for that RP 106 is reset.

As a result of such contraction demand processing, the contractiondemand for the current UE 110 will be taken into account during thecontraction and expansion calculations of other UEs 110 and willinfluence the contraction and expansion of the cQSVs of the other UEs110.

When the current RRC connection is complete (checked in block 436 shownin FIG. 4B), the cQSV for the current UE 110 is stored for possiblelater retrieval and use as described above (block 438).

The various techniques described above can be used to more effectivelymanage the simulcast zone used for transmitting to each UE connected toa cell provided by a C-RAN.

FIGS. 5A-5B comprise a flow chart illustrating one exemplary embodimentof a method 500 of dynamically managing a link adaptation variable usedto initialize and dynamically update the modulation and coding scheme(MCS) used to communicate with a UE in a C-RAN. The embodiment of method500 shown in FIGS. 5A-5B is described here as being implemented in theC-RAN system 100 of FIG. 1 , though it is to be understood that otherembodiments can be implemented in other ways.

The blocks of the flow diagram shown in FIGS. 5A-5B have been arrangedin a generally sequential manner for ease of explanation; however, it isto be understood that this arrangement is merely exemplary, and itshould be recognized that the processing associated with method 500 (andthe blocks shown in FIGS. 5A-5B) can occur in a different order (forexample, where at least some of the processing associated with theblocks is performed in parallel and/or in an event-driven manner).

Method 500 is described here as being performed for each UE 110 that isconnected to the cell 103. The particular UE 110 for which method 500 isbeing performed is referred to here as the “current” UE 110.

In this embodiment, the MCS for each UE 110 is determined using anestimate of the SINR (SINR_(EST)) for that UE 110. This SINR_(EST) isdetermined by adjusting an initial estimate of the SINR for the UE 110(SINR_(EST0)) by a link adaptation variable (Δ_(dB)) maintained for eachcode word used for communicating with that UE 110. That is,SINR_(EST)=SINR_(EST0)+Δ_(dB).

When the current UE 110 establishes a new RRC connection to the cell 103(block 502 shown in FIG. 5A), the link adaptation process is initializedand the link adaptation variable Δ_(dB) for each code word isinitialized (for example, to 0) (block 504).

Then, the link adaptation variables Δ_(dB) are updated each time thereis a HARQ transmission received for the current UE 110 (checked in block506).

In this exemplary embodiment, for each UE 110, the controller 104instantiates a flag (Stale UE flag) for each code word and associatedlink adaptation variable Δ_(dB). Each Stale UE flag is used to determinewhen the associated link adaptation variable Δ_(dB) is stale and shouldbe reset.

When a HARQ transmission is received for the current UE 110 (block 506),if a Stale UE flag is set for an associated code word (checked in block508), the link adaptation variable Δ_(dB) for the associated code wordis reset (for example, to 0) (block 510) and the associated Stale UEflag is cleared (block 512). In some implementations, the linkadaptation variable Δ_(dB) is reset on a conditional basis—for example,only if the link adaptation variable Δ_(dB) is positive.

In this exemplary embodiment, if no initial HARQ transmission hasoccurred for a code word for a configurable number of TTIs (that is, thecorresponding link adaptation variable Δ_(dB) is stale) (checked inblock 514 of FIG. 5B), the associated Stale UE flag is set (block 516),which causes the associated link adaptation variable Δ_(dB) to be resetat the next HARQ transmission.

In this exemplary embodiment, when a new CQI/PMI report is receivedafter an RI change for the current UE 110 (block 518 of FIG. 5B), theStale UE flags for the associated code words are set (block 516), whichcauses the associated link adaptation variables Δ_(dB) to be reset atthe next HARQ transmission.

In this exemplary embodiment, the link adaptation variable Δ_(dB) foreach code word is not reset upon a change in the cQSV for thecorresponding UE 100 or solely in response to a PMI change.

At each HARQ transmission, if the associated link adaptation variablesΔ_(dB) are not reset, the associated link adaptation variables Δ_(dB)are updated based on whether a HARQ ACK or NACK message is received.

As shown in FIG. 5A, if a HARQ ACK is received (checked in block 520),the associated link adaptation variables Δ_(dB) are increased by a firstconfigurable amount (Δ_(ACK)) (block 522). If instead a HARQ NACK isreceived, the associated link adaptation variables Δ_(dB) are decreasedby a second configurable amount (Δ_(NACK)) (block 524). In one example,Δ_(ACK) is set to 0.1 dB and Δ_(NACK) is set to 0.9 db. In someimplementations, Δ_(ACK) and Δ_(NACK) can be updated dynamically.

In this exemplary embodiment, as shown in FIG. 5B, the associated linkadaptation variables Δ_(dB) are adjusted (block 528) upon updating ofthe SINR_(EST0) for the current UE 110 (for example, to reflect a changein CQI or SIRPL) (block 526). The amount of adjustment depends, in thisembodiment, on the number of HARQ ACK or NACK based updates that havebeen made since the last adjustment. In one example, each adjusted linkadaptation variable Δ_(dB_new)=that link adaptation variable beforeadjustment Δ_(dB_old)+f*X, where:

X=the SINR_(EST0) for the link adaptation variable before adjustmentΔ_(dB_old) minus the SINR_(EST0) for the adjusted link adaptationvariable Δ_(dB_adjusted); and

f=the minimum of (a) the number of ACK/NACK based updates that have beenmade since the last adjustment divided by a configurable maximum numberof ACK/NACK based updates that have been made since the last adjustment;or (b) 1.

In this exemplary embodiment, except for retransmissions, no rankoverride is used (even when there is little buffered data to transmit).The dynamic cQSV scheme that is used can be designed to minimize theconditions where a rank override may be necessary. If retransmission isrequired, the same transport format as the initial transmission is used,regardless of the prevailing rank at the time of retransmission.

The methods and techniques described here may be implemented in digitalelectronic circuitry, or with a programmable processor (for example, aspecial-purpose processor or a general-purpose processor such as acomputer) firmware, software, or in combinations of them. Apparatusembodying these techniques may include appropriate input and outputdevices, a programmable processor, and a storage medium tangiblyembodying program instructions for execution by the programmableprocessor. A process embodying these techniques may be performed by aprogrammable processor executing a program of instructions to performdesired functions by operating on input data and generating appropriateoutput. The techniques may advantageously be implemented in one or moreprograms that are executable on a programmable system including at leastone programmable processor coupled to receive data and instructionsfrom, and to transmit data and instructions to, a data storage system,at least one input device, and at least one output device. Generally, aprocessor will receive instructions and data from a read-only memoryand/or a random access memory. Storage devices suitable for tangiblyembodying computer program instructions and data include all forms ofnon-volatile memory, including by way of example semiconductor memorydevices, such as EPROM, EEPROM, and flash memory devices; magnetic diskssuch as internal hard disks and removable disks; magneto-optical disks;and DVD disks. Any of the foregoing may be supplemented by, orincorporated in, specially-designed application-specific integratedcircuits (ASICs).

A number of embodiments of the invention defined by the following claimshave been described. Nevertheless, it will be understood that variousmodifications to the described embodiments may be made without departingfrom the spirit and scope of the claimed invention. Accordingly, otherembodiments are within the scope of the following claims.

Example Embodiments

Example 1 includes a system to provide wireless service comprising: acontroller; and a plurality of radio points; wherein each of the radiopoints is associated with at least one antenna and remotely located fromthe controller, wherein the plurality of radio points is communicativelycoupled to the controller; wherein the controller and the plurality ofradio points are configured to implement a base station in order toprovide wireless service to a plurality of user equipment (UEs) using acell; wherein the controller is communicatively coupled to a corenetwork of a wireless service provider; wherein the system is configuredto transmit at least some data to each UE connected to the cell using arespective subset of the radio points; wherein the system is configuredto determine the respective subset of the radio points for transmittingto each UE connected to the cell using a signature vector comprising aset of signal reception metrics, each signal reception metric associatedwith a respective one of the radio points and indicative of thereception of a signal transmitted from the respective UE at one of theradio points; and wherein the system is configured to do the followingwhen each UE establishes a new connection with the cell: determineinitial signal reception metrics for that UE; and if the system has astored signature vector associated with that UE and that storedsignature vector matches the initial signal reception metrics for thatUE, initialize the signature vector for that UE using that storedsignature associated with that UE.

Example 2 includes the system of Example 1, wherein the system isconfigured to store the signature vector associated with each UEconnected to the cell when each connection that UE establishes with thecell is completed.

Example 3 includes the system of any of the Examples 1-2, wherein thesystem is configured to determine the initial signal reception metricsfor each UE connected to the cell based on a LTE Physical Random AccessChannel (PRACH) transmission from that UE.

Example 4 includes the system of any of the Examples 1-3, wherein thesystem is configured to update the signature vector for each UEconnected to the cell based on LTE Sounding Reference Signals (SRS)transmitted by that UE.

Example 5 includes the system of any of the Examples 1-4, wherein thecontroller is communicatively coupled to the radio points using aswitched ETHERNET network.

Example 6 includes a system to provide wireless service comprising: acontroller; and a plurality of radio points; wherein each of the radiopoints is associated with at least one antenna and remotely located fromthe controller, wherein the plurality of radio points is communicativelycoupled to the controller; wherein the controller and the plurality ofradio points are configured to implement a base station in order toprovide wireless service to a plurality of user equipment (UEs) using acell; wherein the controller is communicatively coupled to a corenetwork of a wireless service provider; wherein the system is configuredto do the following for each UE connected to the cell: determine asignature vector comprising a set of signal reception metrics, eachsignal reception metric associated with a respective one of the radiopoints and indicative of the reception of a signal transmitted from therespective UE at one of the radio points; determine a respective minimumsubset of the radio points for transmitting to that UE; determine arespective maximum subset of the radio points for transmitting to thatUE; and determine a respective current subset of the radio points fortransmitting to that UE based on, at least, the signature vector, therespective minimum subset of the radio points for transmitting to thatUE, and the respective maximum subset of the radio points fortransmitting to that UE; wherein the system is configured to, for eachUE connected to the cell, expand the number of radio points in theminimum subset of the radio points if the respective signature vectorfor that UE has not been updated at least a predetermined number oftimes; and wherein the system is configured to wirelessly transmit atleast some data to each UE connected to the cell using the respectivecurrent subset of the radio points determined for that UE based.

Example 7 includes the system of Example 6, wherein the system isconfigured to store the signature vector associated with each UE wheneach connection that UE establishes with the cell is completed; andwherein the system is configured to do the following when each UEestablishes a new connection with the cell: determine initial signalreception metrics for that UE; and if the system has a stored signaturevector associated with that UE and that stored signature vector matchesthe initial signal reception metrics for that UE, initialize thesignature vector for that UE using that stored signature associated withthat UE.

Example 8 includes the system of Example 7, wherein the system isconfigured to determine the initial signal reception metrics for each UEbased on a LTE Physical Random Access Channel (PRACH) transmission fromthat UE.

Example 9 includes the system of any of the Examples 6-8, wherein thesystem is configured to update the signature vector for each UE based onLTE Sounding Reference Signals (SRS) transmitted by that UE.

Example 10 includes the system of any of the Examples 6-9, wherein thesystem is configured to expand the number of radio points in the minimumsubset of the radio points for each UE using a phased approach if therespective signature vector for that UE has not been updated at least apredetermined number of times.

Example 11 includes the system of any of the Examples 6-10, wherein thecontroller is communicatively coupled to the radio points using aswitched ETHERNET network.

Example 12 includes the system of any of the Examples 6-11, wherein thesystem is configured to do the following for each UE connected to thecell: determine a modulation and coding scheme (MCS) to use with eachcode word used for communications with said UE as a function of anestimate of a signal-to-interference-plus-noise ratio (SINR) and a linkadaptation variable associated with each code word; and dynamicallyupdate each link adaptation variable for said UE based on hybridautomatic repeat request (HARQ) acknowledgments (ACKs) and negativeacknowledgements (NACKs) received for said UE and the associated codeword.

Example 13 includes a system to provide wireless service comprising: acontroller; and a plurality of radio points; wherein each of the radiopoints is associated with at least one antenna and remotely located fromthe controller, wherein the plurality of radio points is communicativelycoupled to the controller; wherein the controller and the plurality ofradio points are configured to implement a base station in order toprovide wireless service to a plurality of user equipment (UEs) using acell; wherein the controller is communicatively coupled to a corenetwork of a wireless service provider; wherein the system is configuredto do the following for each UE connected to the cell: determine asignature vector comprising a set of signal reception metrics, eachsignal reception metric associated with a respective one of the radiopoints and indicative of the reception at one of the radio points of asignal transmitted from the respective UE; determine a respectiveminimum subset of the radio points for transmitting to that UE;determine a respective maximum subset of the radio points fortransmitting to that UE; and determine a respective current subset ofthe radio points for transmitting to that UE based on, at least, thesignature vector, the respective minimum subset of the radio points fortransmitting to that UE, and the respective maximum subset of the radiopoints for transmitting to that UE; wherein the system is configured to,for each UE connected to the cell, update the respective current subsetof the radio points used to transmit that UE based on at least one ofthe following: at least one ratio of the actual rate of throughput forat least one UE connected to the cell and an estimated rate ofthroughput for said at least one UE connected to the cell; at least oneprocessing load at the radio points; and demand from at least one UEconnected to the cell to use at least one radio point; and wherein thesystem is configured to wirelessly transmit at least some data to eachUE connected to the cell using the respective current subset of theradio points determined for that UE.

Example 14 includes the system of Example 13, wherein the system isconfigured to, for each UE connected to the cell, expand the number ofradio points in the respective current subset of the radio points forthat UE if that UE experiences issues receiving transmissions using thecurrent subset of the radio points.

Example 15 includes the system of any of the Examples 13-14, wherein thesystem is configured to store the current subset of the radio points foreach UE when each connection that UE establishes with the cell iscompleted; and wherein the system is configured to, when each UEestablishes a new connection with the cell, initialize the currentsubset of the radio points for that UE if there is a stored currentsubset of the radio points for that UE and if certain conditions aremet.

Example 16 includes the system of any of the Examples 13-15, wherein thesystem is configured to, for each UE connected to the cell, expand thenumber of radio points in the minimum subset of the radio points if therespective signature vector for that UE has not been updated at least apredetermined number of times.

Example 17 includes the system of any of the Examples 13-16, wherein thesystem is configured to determine the initial signal reception metricsfor each UE based on a LTE Physical Random Access Channel (PRACH)transmission from that UE.

Example 18 includes the system of any of the Examples 13-17, wherein thesystem is configured to update the signature vector for each UE based onLTE Sounding Reference Signals (SRS) transmitted by that UE.

Example 19 includes the system of any of the Examples 13-18, wherein thecontroller is communicatively coupled to the radio points using aswitched ETHERNET network.

Example 20 includes the system of any of the Examples 13-19, wherein thesystem is configured to do the following for each UE connected to thecell: determine a modulation and coding scheme (MCS) to use with eachcode word used for communications with said UE as a function of anestimate of a signal-to-interference-plus-noise ratio (SINR) and a linkadaptation variable associated with that code word; and dynamicallyupdate each link adaptation variable for said UE based on hybridautomatic repeat request (HARQ) acknowledgments (ACKs) and negativeacknowledgements (NACKs) received for said UE and the associated codeword.

What is claimed is:
 1. A system to provide wireless service comprising: a controller; and a plurality of radio points; wherein each of the radio points is associated with a respective at least one antenna, wherein the plurality of radio points is communicatively coupled to the controller; wherein the system is configured to use the controller and the plurality of radio points to implement a base station in order to provide wireless service to a plurality of user equipment (UEs) using a cell; wherein the system is configured to do the following for each UE connected to the cell: determine a respective signature vector for that UE comprising a set of signal reception metrics determined for that UE, each signal reception metric associated with a respective one of the radio points; determine a respective minimum subset of the radio points for transmitting to that UE; and determine a respective current subset of the radio points for transmitting to that UE based on, at least, the signature vector and the respective minimum subset of the radio points for transmitting to that UE, the respective current subset for that UE having a respective number of radio points included therein; wherein the system is configured to, for each UE connected to the cell, expand the respective number of radio points in the respective minimum subset of the radio points for that UE if the respective signature vector for that UE has not been updated at least a predetermined number of times; and wherein the system is configured to wirelessly transmit respective data to each UE connected to the cell using the respective current subset of the radio points determined for that UE.
 2. The system of claim 1, wherein the system is configured to store the respective signature vector associated with each UE when each connection that UE establishes with the cell is completed; and wherein the system is configured to do the following when each UE establishes a new connection with the cell: determine respective initial signal reception metrics for that UE; and if the system has a respective stored signature vector associated with that UE and that respective stored signature vector matches the respective initial signal reception metrics for that UE, initialize the respective signature vector for that UE using that respective stored signature associated with that UE.
 3. The system of claim 2, wherein the system is configured to determine the respective initial signal reception metrics for each UE based on a Physical Random Access Channel (PRACH) transmission from that UE.
 4. The system of claim 1, wherein the system is configured to update the respective signature vector for each UE based on Sounding Reference Signals (SRS) transmitted by that UE.
 5. The system of claim 1, wherein the system is configured to expand the respective number of radio points in the respective minimum subset of the radio points for each UE using a phased approach if the respective signature vector for that UE has not been updated at least a predetermined number of times.
 6. The system of claim 1, wherein the controller is communicatively coupled to the radio points using a switched ETHERNET network.
 7. The system of claim 1, wherein the system is configured to do the following for each UE connected to the cell: determine a respective modulation and coding scheme (MCS) to use with each code word used for communications with that UE as a function of an estimate of a signal-to-interference-plus-noise ratio (SINK) and a link adaptation variable associated with each code word; and dynamically update a respective link adaptation variable for that UE based on hybrid automatic repeat request (HARQ) acknowledgments (ACKs) and negative acknowledgements (NACKs) received for that UE and the associated code word.
 8. The system of claim 1, wherein the system is configured to do the following for each UE connected to the cell: determine a respective maximum subset of the radio points for transmitting to that UE; and wherein the respective current subset of the radio points for transmitting to each UE connected to the cell is determined based on, at least, the respective signature vector for that UE, the respective minimum subset of the radio points for transmitting to that UE, and the respective maximum subset of the radio points for transmitting to that UE.
 9. The system of claim 1, wherein each of the radio points is remotely located from the controller.
 10. The system of claim 1, wherein, for the respective signature vector for each UE connected to the cell, each signal reception metric of the respective signature vector is indicative of reception at the associated one of the radio points of a signal transmitted from that UE.
 11. A system to provide wireless service comprising: a controller; and a plurality of radio points; wherein each of the radio points is associated with a respective at least one antenna, wherein the plurality of radio points is communicatively coupled to the controller; wherein the system is configured to use the controller and the plurality of radio points to implement a base station in order to provide wireless service to a plurality of user equipment (UEs) using a cell; wherein the system is configured to do the following for each UE connected to the cell: determine a respective signature vector for that UE comprising a set of signal reception metrics determined for that UE, each signal reception metric associated with a respective one of the radio points; determine a respective minimum subset of the radio points for transmitting to that UE; and determine a respective current subset of the radio points for transmitting to that UE based on, at least, the respective signature vector and the respective minimum subset of the radio points for transmitting to that UE, the respective current subset for that UE having a respective number of radio points included therein; wherein the system is configured to, for at least one UE connected to the cell, update the respective current subset of the radio points used to transmit to said at least one UE based on at least one ratio of the actual rate of throughput for said at least one UE and an estimated rate of throughput for said at least one UE; and wherein the system is configured to wirelessly transmit respective data to each UE connected to the cell using the respective current subset of the radio points determined for that UE.
 12. The system of claim 11, wherein the system is configured to, for each UE connected to the cell, expand the respective number of radio points in the respective current subset of the radio points for that UE if that UE experiences issues receiving transmissions using the respective current subset of the radio points.
 13. The system of claim 11, wherein the system is configured to store the respective current subset of the radio points for each UE when each connection that UE establishes with the cell is completed; and wherein the system is configured to, when each UE establishes a new connection with the cell, initialize the respective current subset of the radio points for that UE if there is a respective stored current subset of the radio points for that UE and if certain conditions are met.
 14. The system of claim 11, wherein the system is configured to, for each UE connected to the cell, expand the respective number of radio points in the respective minimum subset of the radio points for that UE if the respective signature vector for that UE has not been updated at least a predetermined number of times.
 15. The system of claim 11, wherein the system is configured to determine respective initial signal reception metrics for each UE based on a Physical Random Access Channel (PRACH) transmission from that UE.
 16. The system of claim 11, wherein the system is configured to update the respective signature vector for each UE based on Sounding Reference Signals (SRS) transmitted by that UE.
 17. The system of claim 11, wherein the controller is communicatively coupled to the radio points using a switched ETHERNET network.
 18. The system of claim 11, wherein the system is configured to do the following for each UE connected to the cell: determine a respective modulation and coding scheme (MCS) to use with each code word used for communications with that UE as a function of an estimate of a signal-to-interference-plus-noise ratio (SINK) and a link adaptation variable associated with that code word; and dynamically update a respective link adaptation variable for that UE based on hybrid automatic repeat request (HARQ) acknowledgments (ACKs) and negative acknowledgements (NACKs) received for that UE and the associated code word.
 19. The system of claim 11, wherein the system is configured to do the following for each UE connected to the cell: determine a respective maximum subset of the radio points for transmitting to that UE; and wherein the respective current subset of the radio points for transmitting to each UE connected to the cell is determined based on, at least, the respective signature vector for that UE, the respective minimum subset of the radio points for transmitting to that UE, and the respective maximum subset of the radio points for transmitting to that UE.
 20. The system of claim 11, wherein each of the radio points is remotely located from the controller.
 21. The system of claim 11, wherein, for the respective signature vector for each UE connected to the cell, each signal reception metric of the respective signature vector is indicative of reception at the associated one of the radio points of a signal transmitted from that UE. 